Process for the separation of pith and fiber components of bagasse



Sept. 3, 1957 J. H. PAYNE l-:TAL 2,805,156

PROCESS FOR THE SEPARATION OF PITH AND FIBER COMPONENTS OF BAGASSE FlledJan 21, 1953 2 Sheets-Sheet l amsn/Ne V61@ 77694 SKU/NG .14E/V496JMAZ/JON INVENTORS Sept.y 3, 1957 Filed Jan. 21, 1953 J. H. PAYNE ET A.PROCESS FOR THE SEPARATION OF PITH AND FIBER COMPONENTS BAGASSE- 2Sheets-Sheet 2.

He. Z.

. #Trae/vias PROCESS FR THE SEPARATEN GF PIT H AND FBER COMPNENTS FBAG-ASSE John H. Payne, William Kenda, and Henry l. Mahon, Honolulu,Territory of Hawaii, assignors, by mesne assignments, to HawaiianDevelopment Qompany, ist-rl., Honolulu, Territory of Hawaii, acorporation of the Territory of Hawaii Application `annary 21, 1953,Serial No. 332,276

4 Claims. (Cl. 92-14) To accomplish this, it is desirable to remove fromtheV bagasse a major portion of the undesirable pithy component and toeliminate the large quantity of occluded dirt and insoluble matter whichalways accompanies bagasse, due to the conditions under which the sugarcane is harvested. One of the principal objects of this invention is,

then, to provide a process for the separation from bagasse of cleanfiber suitable for paper pulp production.

Another object of this invention is to provide a process for theseparation of pith and fiber components of bagasse, in which process aminimum amount of tine bagasse liber is produced, and which processprovides substantially complete removal of objectionable ash impuritiesfrom the bagasse fiber.

Still another object of this invention is to provide an eiiicient andrelatively inexpensive process for the separation from bagasse of aliber suitable for the production of paper pulp and dissolving pulp.

Other objects and advantages of this invention, it is believed, will bereadily apparent from the following detailed description of a preferredembodiment thereof when read in connection with the accompanyingdrawings.

In the drawings:

Figure 1 is a flow sheet illustrating a process which comprises apreferred embodiment of this invention.

Figure 2 is a diagrammatic vertical section of a swing hammerdisintegrator utilized in carrying out the preferred process of thisinvention.

Figure 3 is a sectional view, taken substantially on the line 3 3 ofFigure 2.

Referring now to the drawings, and particularly to Figure l, it will beseen that bagasse, which is in the moist condition in which it isusually delivered from the sugar mill, is charged into a cooker whichmay comprise a conventional pulp mill digester, pulper or vegetableblancher. mixture is heated by means of steam and maintained at thedesired temperature for a given period of time. It has been found thatthe addition of from about 0.5 to

about 6 percent caustic soda, based on the dry weight of The bagasse isimmersed in water, and thek Patented Sept. 3, 1957 the bagasse at thetime of its introduction into the cooking equipment. In operation, wehave found optimum results are obtained when the bagasse is cooked forabout one hour at a temperature of from 190400"V F. with a caustic sodaconcentration of 3-6 percent, based on the dry weight of bagasse. Undersome conditions, a cooking period of about thirty minutes issufficiently long.-

The temperature should be maintained in excess of 150 F., but at, ornear, such temperature, a longer cooking period is desirable. Theconsistency of the bagasse during cooking may be varied over a widerange preferably from about 2 to about 7.5 percent.

After cooking, the cooked bagasse stock is diluted with water in awashing and dilution tank, as shown in Figure 1. Preferably, suflicientwater is added to bring the consistency down to about 2 percent or less.tent to which dilution is carried out depends upon the amount of dirtthe original bagasse contains. Where excessive amounts of dirt arepresent, it is desirable to dilute the stock to a consistency of 1percent or less, washing out the large dirt particles to the sewerthrough a screen (not shown) in the dilution tank prior to furi therprocessing.

The cooked and diluted bagasse stock is then pumped to a vertical swinghammer disintegrator generally indicated 10, where the simultaneousdisintegration of the bagasse i. e., loosening of the pith anddirtcomponents from the fiber and separation of the fiber from the pith anddirt particles is carried out.

Referring in particular to Figures 2 and 3, the disintegrator 10 isprovidedl with a screw-type feeder conveyor 11, the outlet of whichleads into the casing 12 of the disintegrator proper. A vertical shaft14 is suitably journaled in the casing, yand is connected in drivenrelation with the drive shaft 16 of a motor 17 by means? of a coupling18. The casing l2 is provided with an annular outwardly-extendingshoulder 20, depending from which is a cylindrical housing 21,downwardly` through which extends the shaft 14. A plurality of swinghammers 25 are pivotally connected to flanges 26 secured to the shaft.Surrounding the swing hammers 25', and closely adjacent the `outer endsthereof, is a cylindrical screen 30.

Connected to the bottom of the housing 2l, and to the bottom of thescreen 30, is a double-walled body por- I tion 32, and dependingtherefrom is a separating discharge device 33 which includes an outerfrusto-conical section 34 communicating with the annular space 35between the screen 30 and housing 21. Centrally of the section34, andcommunicating with the central chamber defined by the screen 30, is aproduct discharge section 36 which is connected to an outlet conduit 38.

Wash water is introduced into the conveyor 11 by means of the pair ofspray heads'40. Additional wash water is applied to the operatingsection of the disintegrator by means of three spaced spray heads 41which are directedupwardly as shown through the agency of the elbowfittings 43. The use of Wash water at these points improves theseparation of the pith and liber and also facilitates the removal ofdirt particles.

Preferably, the screen is provided with perforations of about 1/16 inchdiameter, although perforations of 1/32 inch and '/32 inch have beenused successfully. A shaft speed of 3,600 R. P. M. appears to producethe most desirable fiber product, although satisfactory results havebeen obtained at a speed of 1,800 R. P. M.

The cooked and diluted bagasse stock is pre-broken by The exwardlythrough the screen perforations by continued centrifugal force. Thesedirt and pith particulars are discharged downwardly through the section34 and there discarded. The fiber is retained on the interior Vof thescreen, and then falls downwardly through the discharge section 36, fromWhere it is conveyed through the conduit 38 to be stored for furtherprocessing in accordance with conventional paper mill practice.

By the use of the above-described process, a high recovery of clean,acceptable fiber is obtained. The cooking step produces sufficientsoftening of the libre bundles so that the action of the disintegratordoes not reduce the fiber length to an undesirable extent, yet enablesefficient separation of the undesirable pith and other foreign matter.

It will be readily apparent to those skilled in the art that ash anddirt particles are undesirable components of pulp for paper and viscoseproducts. In the utilization of dissolving pulp for viscose production,the presence of substantial amounts of manganese, copper, and iron inthe pulp has a deleterious effect on the Yviscosity of the resultingviscose. We have found that the process herein described removes asubstantial portion of the soil ash which contains these offendingimpurities. The ash removal obtained with the present process is -muchgreater than that achieved by normal digestion and pulping methodsheretofore recommended for bagasse pith and fiber separation.

Tables I and Il below provide specific examples of the efficacy of theprocess of this invention in removing ash impurities, as compared toother processes.

Table I Ash, FezOa, Cop- Man: Material (Dry Basis) perperper, ganese,

cent cent per percent cent 1. Mill bagasse 2.26 .216 .0010 .0029 2. DryScreened ber 1. 72 250 V.0048 .0022 3. Pulped (3% NaOH, 190 F.) and wetscreened ber 0. 86 .044 .0007 .0008 4. Our process 0.48 .030 .0003 .0003

Table Il Ash, FerOa, Cop- Man- Material (Dry Basis) perperper, ganese,

cent cent' perpercent cent 1. Pulped (6% NaOH, 200 F.) and wet screenediiber 2.13 328 .0060 .0028 2. Our process 0. 68 020 .0002 .0008

Material No. l in Table I was obtained from the discharge roll of thelast mill in a cane sugar factory. Material No. 2 was obtained bypassing mill bagasse containing 45 percent moisture over a l2-mesh Rotexscreen. Material No. 3 was produced by pulping mill bagasse in a.standard pulp mill pulper for one hour in a solution containing 3percent caustic soda based on the dry weight of the bagasse at 190 F.,and then wet screening the pulped stock in a rotary screen to producethe fiber. Material No. 4 was produced by the process of this invention,the cooking stage being carried out in a pulper for one hour in 3percent caustic soda at 190 F.

Materials Nos. l and 2 of Table II correspond to Nos. 3 and y4,respectively, of Table with the exception that, in both of the formercases, the cooking conditions were 200 F., the solution containing 6percent caustic soda based on the dry weight of the bagasse.

The above description and examples are intended to be illustrative only.Any modification of or variation therefrom which conforms to the spiritof the invention is intended to be included within the scope of theclaims.

We claim:

l. In a process for the treatment o f bagasse wherein the bagasse iscooked in an aqueous medium for a sufficient length of time to produce amaterial containing softened bagasse fibers, bagasse pith and foreignmatter, the steps of continuously advancing said material while in a wetcondition downwardly through a zone of disintegration surrounded by asubstantially vertical screen while `directing sprays of water into saidzone, subjecting the material in said zone simultaneously to impactdisintegration, centrifugal attrition and continuous washing action sothat the pith and foreign matter are loosened from the fibers withoutsubstantial disintegration of such fibers and are forced outwardlythrough Vthe perforations of said vertical screen, the fibers beingretained within said zone by said screen and passing generallyVdownwardly through said zone, discharging the pith and foreign matterpassing outwardly through said screen, and separately discharging thedownwardly moving fiber relatively free of pith and foreign matter vfromthe lower end of said zone.

2. In a process for the treatment of bagasse wherein the bagasse iscooked in an aqueous medium for a sufficient length of time to produce amaterial containing softened bagasse fibers, bagasse pith and foreignmatter, the steps of continuously advancing said material while in a wetcondition downwardly through a Zone of disintegration surrounded by avertical screen against upwardly directed sprays of water, subjectingthe material in said zone simultaneously to impact disintegration,centrifugal attrition and continuous washing action so that the pith andforeign matter are loosened from the fibers without substantialdisintegration of such fibers and are forced outwardly through thepcrforations of said vertical screen, the fibers being retained withinsaid zone by said screen and passing generally downwardly, discharging,-the pith and foreign matter passing outwardly through said screen, andseparately discharging the downwardly moving fiber relatively free ofpith and foreign matter from the lower end of said zone.

3. In a process for the treatment of bagasse wherein the bagasse iscooked in an aqueous medium for a sufficient length of time to produce amaterial containing softened bagasse fibers, bagasse pith and foreignmatter, the steps of diluting said material with water to a consistencyof less than 2 percent, continuously advancing said material while in awet condition downwardly through a zone of disintegration surrounded bya vertical screen against upwardly directed sprays of water, subjectingthe material in said zone simultaneously to impact disintegration,centrifugal attrition and continuous washing action so that the'pith andforeign matter are loosened from the fibers without substantialdisintegration of such bers and are forced outwardly through theperforations of said vertical screen, the fibers being retained withinsaid zone by said screen and passing generally downwardly, dischargingthe pith and foreign matter passing outwardly through said screen, andseparately discharging the downwardly moving fiber relatively free 0fpith and foreign matter from the lower end of said zone.

4. In a process for the treatment of bagasse wherein the bagasse iscooked in an aqueous medium for a sufficient length of time to produce amaterial containing softened bagasse fibers, bagasse pith and foreignmatter, the steps of continuously advancing said material while in a wetcondition downwardly through a zone of disintegration while directingsprays of water into said zone, subjecting the material in said zonesimultaneously to impact disintegration, centrifugal attrition andcontinuous washing action so that the pith and foreign matter areloosened from the fibers without substantial disintegration of suchfibers and are forced outwardly from said zone, the fibers beingretained within said zone and passing generally downwardly through saidzone, dis-l charging tlie pith and foreign matter passing outwardly fromsaid zone, and separately discharging the down,-

5 wardly moving fiber relatively free of pith and foreign 1,825,307matter from the lower end of said zone. 1,993,214 2,347,716 ReferencesCited in the le of this patent UNITED STATES PATENTS 5 731,290 DrewsenJune 16, 1903 312,554 799,434 Baker er a1 sept. 12, 1905 501,999 853,943Drewsen May 14, 1907 1,083,102 Jackson Dec. 30, 1913 lo 1,199,241 BurtonSept. 26, 1916 1,656,829 Price Jan. 17, 192s and 35. 1,785,840 MunroeDec. 23, 1930 6 Darling Sept. 29, 1931 Hass Mar. 5, 1935 Staege May 2,1944 FOREIGN PATENTS Germany May 28, 1919 Great Britain Mar. 9, 1939OTHER REFERENCES Wells et al.: Paper Trade J., Mar. 27, 1941, pp. 34

1. IN A PROCESS FOR THE TREATMENT OF BAGASSE WHEREIN THE BAGASSE ISCOOKED IN AN AQUEOUS MEDIUM FOR A SUFFICIENT LENGTH OF TIME TO PRODUCE AMATERIAL CONTAINING SOFTENED BAGASSE FIBERS, BAGASSE PITH AND FOREIGHMATTER, THE STEPS OF CONTINOUSLY ADVANCING SAID MATERIAL WHILE IN A WETCONDITION DOWNWARDLY THROUGH A ZONE OF DISINTEGRATION SURROUNDED BY ASUBSTANTIALLY VERTICAL SCREEN WHILE DIRECTING SPRAYS OF WATER INTO SAIDZONE, SUBJECTING THE MATERIAL IN SAID ZONE SIMULTANEOUSLY TO IMPACTDISINTEGRATION, CENTRIFUGAL ATTRITION AND CONTINUOUS WASHING ACTION SOTHAT THE PITCH AND FOREIGH MATTER ARE LOOSENED FROM THE FIBERS WITHOUTSUBSTANTIAL DISINTEGRATION OF SUCH FIBERS AND ARE FORCED OUTWARDLYTHROUGH THEE PERFORATIONS OF SAID VERTICAL SCREEN, THE FIBERS BEINGRETAINED WITHIN SAID ZONE BY SAID SCREEN AND PASSING GENERALY DOWNWARDLYTHROUGH SAID ZONE, DISCHARGING THE PITH AND FOREIGN MATTER PASSINGOUTWARDLY THROUGH SAID SCREEN, AND SEPARATELY DISCHARGING THE DOWNWARDLYMOVING FIBER RELATIVELY FREE OF PITH AND FOREIGN MATTER FROM THE LOWEREND OF SAID ZONE.